Insulated conductor



Dec. 12, 1933. J. w. GREENLEAF INSULATED CONDUCTOR- Filed'Dec.

2 Sheets-Sheet 1 Dec. 12, 1933. J. w GREENLEAF 1,938,626

INSULATED CONDUCTOR Filed Dec. 13, 1929 2 Sheets-Sheet 2 Patented Dec. 12, 1933 INSULATED CONDUCTOR John W. Greenleaf, Hamden, Conn, alllgnor to Eockbestos Products Corporation, New Haven, Conn a corporation of Massachusetts Application December 13, 1929 Serial No. 413,782

8 Claims. (01. 113-34) This invention relates to insulated conductors, and more particularly to relatively fine or small gauge conductors such as magnet wire, the insulation of which is required to be comparatively thin and flexible, and to be uniform and effective throughout with respect to its insulating properties.

Because of their excellent insulating and fireproofing qualities and their adaptability to be 10 compressed and still retain the required degree.

asbestos fibres have been and are being used toa considerable extent to. form coverings or insulating sheaths for electric conductors of certain types. This material, however, is extremely difilcult to handle and to apply properly to a conductor, especially when this is done commeb cially, in which case it is desired to efilciently insulate a wire quite rapidly in order'to maintain the production costs at a minimum. Rapid handling of this material requires extreme care, and in many instances, delicately operating apparatus in order that the material will not be pulled apart or otherwise separated or broken, and to insure that it will be uniformly applied both in density and thickness about the wire or conductor.

Various methods have been proposed for app y n fibrous material to a conductor. One method was to wind a roving of fibres about'a conductor, to rough up the outer fibres, for instance by brushing them, and then to press the entire covering against a wire thatmay or may not have previously had an adhesive applied thereto. 'Another proposed method was to use a thread reinforced sliver of fibres instead of the roving above mentioned. Still another method proposed the application to the wire of a plu- 40 rality of rovings of fibrous material, either by winding them upon the conductor or disposing them generally parallel thereto and about the same, a separate. thread being supplied with a plurality of rovlngs to prevent pulling strains from breaking the rovings. More recently it has been proposed to apply a sliver of fibres obtained direct from the carding machine, directly upon an adhesive-covered conductor by apparatus that disposed the fibres of the material in a certain arrangement upon the conductor, in order that an especially thin and uniform covering would be obtained.

All of the above proposed methods were to some extent either difilcult to perform, or due to the extreme care required, time consuming, and

if commercial production was possible the cost of production was relatively high although the product resulting therefrom was, in some cases, efiicient in use. In some cases, for instance, when the use of a plurality of rovings was unso dertaken, the resultant covering could not be as thin as was required and there was an inherent tendency for the insulation to open up between windings when the conductor was sharply bent. When insulation is applied in this manner, it is as difilcult or impossible to spread the fibres of adjacent rovings sufficiently to thoroughly intermingle them and thus form a uniformly dense but thin layer, and such a method is not adapted to the manufacture of small conductors such as magnet wire.

This invention contemplates an improvement over all of the above methods of insulating conductors and in the product resulting therefrom by providing a conductor with an insulating covering of the required degree of thinness, uniformity and effectiveness and at an appreciably faster rate of production. .For instance, the present invention has resulted in the covering of Y a conductor with as thin a layer of asbestos a0 fibres as four thousandths (.004) of an inch, which layer is uniform in density and of the required insulation characteristics throughout its length, and in the application of such an insulation approximately four times as fast as any similar insulation, to my knowledge, has ever before been applied. Although asbestos fibres are preferred as the insulating material, other fibrous materials, such for example as cotton fibres, may be used, and therefore it is understood that this invention is not limited to the use of asbestos fibres.

One of the objects of this invention, therefore, is to provide an improved insulated conductor.

Another object is to provide an insulating covering fora conductor of fibrous insulating material applied thereto in such an arrangement or manner that a comparatively thin covering is formed that will be of uniform density and 10 of the required insulating characteristics while being tough, fiexible and capable of withstand- 'ing very considerable lineal and bending strains without fracture or opening up to expose the conductor. Another object is to provide an insulating covering of a conductor with means that will reinforce the covering against lineal strains, which may be applied substantially parallel to the wire and which will also be useful during the operations of applying the covering to reinforce the material thereof, as it is being applied.

To these and other ends, the invention consists in the novel features and combinations of parts to be hereinafter described and claimed.

In the accompanying drawings:

Fig. 1 illustrates the apparatus used for performing one of the preparatory steps in the method of insulating a conductor embodying the features of this invention;

Fig. 2 illustrates apparatus used for performing the other steps and operations in the method of insulating the conductor;

Fig. 3 is a section on line 3--3 of Fig. 2;

Fig. 4 is a section on line 44 of Fig. 2;

Fig. 5 is a composite view showing the relative position of the conductor and the insulating material therefor during the various stages of the application of the latter to the former;

Fig. 6 comprises a plan view and a cross-section thereof showing the relative position of a conductor and the insulating material therefor at substantially the start of the operation performed by the apparatus shown in Fig. 2;

Fig. 7 shows a longitudinal section and a cross-section of the conductor and the insulation therefor during the application of the latter to the former;

Fig. 8 shows in elevation and in cross-section the completed insulation covered conductor, and

Fig. 9 is a view similar to Fig. 5, but showing the application of a modified form of insulating covering.

Figs. 5 to 9 are greatly enlarged as compared to. the actual product, for the sake of clearness and in order to show in substantially correct proportion the elements of the improved insulated conductor, embodying the features of this invention.

In the drawings, Figs. 1 to 4 inclusive, illustrate the preferred apparatus used in forming and applying the insulating cover. In Fig. 1, the dofler roll 12 of a carding machine is shown delivering, by the action of comb 14, a sliver 13 of asbestos fibres upon a forwardly traveling belt 15. The sliver is laid upon a filamenttary member or thread 16 supported on and moving with the belt. As a result of the forwardly directed movement of the belt and sliver, the thread is unwound from a ball or roll 1'7. The sliver of fibres when delivered to the belt 15 drops upon the thread 16 and with it is fed toward and between a'pair of cooperating rubmotion belts 18 and 19, that by known driving mechanism, are given simultaneously forwardly progressing and relatively lateral movements. The action of the rub-motion belts 18 and 19 upon the sliver l3 and thread 16, causes the fibres to be wrapped about the thread, positioning the thread substantially in the center of the body of fibres, as well as slightly compressing and thoroughly intermingling the fibres. The thread reinforced sliver 20, formed as above described, is then wound upon a reel 21,-during which operation this product is slightly flattened but without disturbing the relative position of the fibres with respect to each other or to the thread 16. The reinforced sliver comprises a thread having a plurality of fibres substantially uniformly surrounding the same and these fibres while interentangled are substantially parallel to the thread, owing to the fact that they have not been displaced to any substantlal extent from their normally parallel position as delivered by the carding machine.

The reel 21 of reinforced sliver 20 is placed adjacent the apparatus shown in Fig. 2, and the sliver 20 is fed up over a guide roller 22, and directed downwardly closely adjacent to and in engagement with a conductor 23. The conductor 23 is also directed downwardly from a guide roller 24, afterhaving been fed thereto from a reel 25. During its passage from reel 25 to the guide roller 24, it is preferred to pass the conductor 23 through an adhesive bath 26 to coat the same with an adhesive. Upon engagement of the thread reinforced sliver 20 with the conductor 23, the substantially parallelly directed fibres directly adjacent the conductor will become secured thereto by being embedded in the adhesive thereon, whereby the conductor will draw the reinforced sliver with it into a rapidly rotating wiper 27. Fig. 5' at 60 and Fig. 6 illustrate the relative positions of the conductor 23 and the thread-reinforced sliver 20 when they are first brought into contact with each other somewhat in advance of the wiper 27, the sliver being preferably substantially tangent to the conductor, as shown. In width the sliver approximates the circumferential dimension of the conductor. There may be slight twisting of the sliver about its own axis but not about the conductor intermediate the upper support and the wiper 2'7. The contacting portion of the sliver is tangential to the conductor, and the wiper 27 wraps this about the conductor.

The wiper 27 may comprise a pair of opposed and resilient fingers 28 and 29, that are mounted upon a spindle 30, to which a pinion 31 is secured. The pinion 31, by means of gearing 32 and a driven shaft 33, suitably arranged, rapidly rotates the wiper 27 causing fingers 28 and 29 to revolve about the sliver 20 and conductor 23, that are being drawn therebetween in a direction substantially parallel to the axis of rotation, whereby the sliver 20 is wrapped about the conductor 23 so as to encircle it completely. The speed of rotation of the wiper 27 may be as high as 1600 R. P. M. The fingers 28 and 29, due to their resiliency, slightly compress the sliver 20, causing the fibres thereof to lie more closely together as well as directing the fibres at the outer portion of the covering substantially circumferentially thereabout. During this wrapping operation the fibres of the sliver 20 that directly engage the conductor 23 when the same, with the sliver 20, first en-. ters between the fingers 28 and 29, are embedded in the adhesive upon the conductor and are held firmly thereby to prevent the movement thereof about the conductor while the outer fibres are being disposed circumferentially and the entire body of fibres is being compressed. The inner fibres of the covering, therefore, are disposed substantially parallel with the conductor 23, as well as with their reinforcing thread 16. Due to the disposition of the thread 16 substantially at the center of the mass of fibres constituting the sliver 20, it will be disposed substantially intermediate the inner and outer fibres, that is,

substantially between the parallelly disposed Fig. 6 show the relation of the sliver to the conductor immediately in advance of the wiper. Fig. 5 at 61 and Fig. 'Iillustrate the appearance of the fibrouscovered conductor after having been acted upon by the wiper 2'1. The thread 16, during the above described operations have been kept taut and has acted as a reinforcement of the fibrous sliver 13, permitting it to be rapidly fed to the conductor 23, and retaining it in position relatively thereto until it is caught upon the adhesive on the conductor and passed through the wiper 27. After this operation, the thread 16 continues to serve as a reinforcement. Due to being taut, the thread or filament 16 tends to prevent the inner fibres from being drawn about the conductor 23 by the action of the wiper 27, especially if the adhesive has not sufficiently dried to retain the same, and further assists in preventing the outer fibres from being removed from the body of fibres by the rapid action of wiper 2'1, due to the binding action of the thread 16 upon the fibres or ends thereof disposed between it and the conductor, it being understood that all of the fibres are indiscriminately intermingled and, therefore, tend to hold each other in place.

- After passing through the wiper 27, the resultant product is directed and fed to a wheel 34,

bath of insulating compound 35, through which the fibrous covered conductor is passed. The

compound 35 is of such nature that it permeates the fibrous covering which, therefore, becomes thoroughly impregnated therewith. The filled fibrous covered conductor is then directed upwardly and passed through a secondwiper 36, which is rapidly rotated due to its attachment upon a spindle 37, that is driven by a pinion 38, secured thereto, which in turn through gearing 39 is driven by shaft 33. The wiper 36, having resilient fingers 40 similar to fingers 23 and 29, rotates about and in engagement with the covering, and by slightly compressing the same forces out the surplus compound while compacting the mass of fibres preparatory to the next operation. The direction of rotation of the wiper 36 relatively to the conductor is the same as that of the wiper 27 and, therefore, the above mentioned disposition of the fibres upon the conductor is not changed or disturbed. Fig. 5 at 62 illustrates the appearance of the fibrous covered conductor after having been acted upon by wiper 36.

The fibre covered conductor during its continued passage upwardly is fed between a pair of opposed polishing plates 41 and 42 of a compacting and surface polishing device 43. The plates 41 and 42 are slidably mounted in a frame 44 for transverse movement relatively to the conductor, being guided in their movements by stems 45 and 46 respectively, disposed in openings 47 and 48, provided in the frame 44. Links 49 and 50 secured to and extending from each stem 45 and 46, are respectively secured to plungers 51 and 52 that are slidably mounted for transverse movement relatively to the conductor and the axis of. the frame 44, in openings provided in the frame. The frame 44 is secured to the spindle" 37 for rotation therewith. Rapid rotation of {the spindle 37 causes centrifugal force to ac upon the plungers 51 and 52 to move them outwardly, which causes links 49 and 50 to pull the plates 41 and 42 radially inwardly and against the covered conductor with sufiicient force to thoroughly compact the fibrous coverhas the appearance illustrated in Fig. 5 at 63 and in Fig. 8, the covering indicated at 53 being composed of'a compact substantially homogeneous mass of entangled fibres, the inner fibres of which are in engagement with and substantially parallel to the conductor 23, and the outer fibres generally circumferentially disposed relatively thereto, and in which mass a reinforcing thread or filament is thoroughly embedded and disposed substantially parallel to the conductor intermediate the parallel inner and circumferentially disposed outer fibres.

The thread 16 in the finished product continues to serve as a-reinforcement for the covering of the completely. covered conductor. Being substantially an integral part of the cover, the thread or filament, due to its undisturbed structure, resists inadvertent and accidental displacement or removal of the covering from the wire or conductor, and extending as it does the entire length of the covering it reinforces the same against lineal strains tending to tear it apart or from the conductor. Preferably the thread forms a comparatively small part of the covering. In the present example, Fig. 5 at 63 and Fig. 8 disclose the thread 16, fibrous cover and conductor 23 substantially proportional to a thread, the diameter of which is approximately .0015 of an inch, a thickness of .004 inch for the finished covering and a diameter of .032 inch for the wire or conductor, which dimensions have been used by me with success in the manufacture of commercial wire. It has been found that advantageous results can be obtained by the use of a #80 single strand, slightly twisted cotton thread, as the reinforcing means, but it will be understood that variations may be made in this respect and that the dimensions and proportions above mentioned can be altered considerably without departure from the invention, although the invention is particularly applicable to the insulation of wire smaller than #14 B 8: S

1 By my invention, an improved insulated conductor as above described may be made several times as rapidly as has ever before been accomplished in the manufacture of a comparable conductor. This obviously is an important result in that a relatively large reduction in production cost is obtained as well as an improved covered conductor structure.

Fig. 9 illustrates at 6'7 the relative position of a conductor 64 and two thread reinforced slivers 65 and 66, when they are first brought into contact with the conductor 64, somewhat in advance of the wiper 27, the slivers being preferably substantially tangent to the conductor and disposed adjacent opposite sides thereof. The appearance of the covered conductor during subsequent stages of the application of insulating material thereon, is illustrated in Fig. 9 at 68, after the covered conductor has passed through the wiper 27, at 69 after it has passed the wiper 36, and at '10 after it has passed the surface polishing device 43. The application of'v part of the subject matter of and are claimed in my copending application, Serial No. 413,783, filed December 13, 1929.

While I have shown and described a preferred embodiment of my invention and a preferred example of the method of making the product, the invention is not to .be limited to all of the details shown, but is capable of modification and variation within the spirit of the invention and within the scope of the appended claims.

What I claim is:

1. An insulated conductor comprising a core member having a compacted mass of felted interentangled fibres thereon, and a reinforcing filament embedded in said mass and extending substantially parallel to said core member the entire length of the covering thereon.

2. An insulated conductor comprising a core member having a thoroughly compacted and substantially homogeneous mass of fibrous insulating material thereon, including a reinforcing filament embedded therein and extending substantially parallel to said core member the entire length of the covering thereon, said reinforcing filament being spaced outwardly from the periphery of said core member and being entirely surrounded and embedded in said mass of fibres.

3. An insulated conductor comprising a core member havinga mass of fibrous insulating material thereon characterized by the fact that the fibres adjacent the conductor are arranged generally parallel thereto, and the fibres adjacent the outer surface of the insulating covering are arranged generally circumferentially thereabout, and including a reinforcing filament embedded in said covering and extending substantially parallel to said core member the entire length of the covering thereon.

4. An insulated conductor comprising a core member having a thoroughly compacted and substantially homogeneous mass of fibrous insulating material thereon characterized by the fact that the fibres adjacent the conductor are arranged generally parallel thereto, and the fibresiadiacent the outer surface of the insulating covering are arranged generally circumferentially thereabout, and including a reinforcing filament embedded therein, and extending substantially parallel to said core member the entire length of the covering thereon, said reinforcing filament being disposed substantially intermediate the parallelly disposed fibres and the circumferentially disposed ones.

5. In an insulated conductor, in combination with a core, an insulating sheath formed of a single untwisted body of interentangled fibres, said body having an internal filament reinforcement of spun fibres extending parallel to the core beneath the outer surface of said sheath substantially continuously throughout the length of the sheath.

6. In an insulated conductor,in combination with a core member, a fibrous body consisting of a single untwisted sliver completely encircling the core member, and a single textile reinforcing filament of substantial length embedded within said fibrous body and extending parallel to said core member adjacent its periphery, said sliver and single filament forming in conjunction a complete sheath for the core member.

'7. A fine magnet wire comprising a core member substantially finer than #14 B 8: S gauge, said core member having a thin longitudinally continuous mass of felted fibres thereon including a reinforcing filament embedded therein and enclosed thereby at one side of the core member, said filament extending substantially continuously the full length of the fibrous covering.

8. Magnet wire comprising a core member having a coat of adhesive and having a thoroughly compacted mass of fibres held in place by said adhesive and including in its structure a reinforcing thread wholly enclosed therein and following a line parallel to the axis of the core member throughout the length thereof.

JOHN W. GREENLEAF. 

